Retargeting to epidermal growth factor receptor improves therapeutic effect of suicide gene therapy. Free

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Adenovirus-mediated gene therapy has been used for uterine cervical cancer, however, the in vivo efficacy has been limited by a lack of tissue specificity and low infection efficiency. To get sufficient transduction of the cervical cancer cells by the adenovirus (Ad) vector, we thought to augment the transduction of cervical cancer cells by re-routing the Ad vector to epidermal growth factor receptor (EGFR) that is expressed at relatively high levels on their surface. EGFR retargeting was accomplished with a bispecific antibody that has two binding specificities. One part of the antibody binds to the fiber of the Ad vector and the other part binds to the EFGR expressed on the surface of cervical cancer cells. Ad vectors were then complexed with the antibodies. The resulting EGFR-targeted Ad was then used to infect cervical cancer cells. We first screened transductional and transcriptional activity of EGFR-targeted adenovirus serotype5 (Ad5) in vitro in HeLa, CaSKi and SiHa cells. The EGFR retargeting Ad5 markedly enhanced efficient gene transfer to these cells compared to the untargeted Ad5, as indicated by the elevated levels of reporter gene expression (in HeLa, CaSKi, and SiHa cells was 4.7-fold, 3.1-fold, and 1.7-fold more, respectively), whereas EGFR negative cell, Mewo, did not show any enhanced transduction. Next, monoclonal antibody 425 (mab 425), which binds the EGFR, was used to block infection and to demonstrate the specificity of EGFR retargeting. The pre-treatment of the cells with mab 425 blocked the EGFR-retargeted adenovirus infection. Thus, we demonstrated that EGFR retargeting augments gene transfer to cervical cancer cells is specifically through EGFR. We finally examined the cytocidal effect with herpes simplex virus thymidine kinase (HSV-TK) gene of EFGR-targeted Ad5 in vitro. In MTS assay, the sensitivity to gancyclovir in cervical cancer cells infected with EGFR-targeted Ad was enhanced compared to that infected with untargeted Ad, whereas the enhancement was not observed in Mewo cells. These results suggest that enhanced transduction of EGFR-targeted adenoviral vectors can improve the therapeutic effect with suicide gene therapy and, on this basis, we considered alternative strategies to achieve efficient gene transfer to these target cells using a modified adenovirus vector. This modification makes the vector potentially more valuable in the clinical setting.